How to solve this pre-increament in c?

Question

I am unable to get the correct answer to this question. Can anyone help me with stepwise explanation?
#include <stdio.h>
#include<math.h>

int main()
{
int a=12,b;
b=++a + ++a + ++a;
printf("%d %d", a,b);
return 0;
}

Answer 1

b = 13 + 14 + 15

Output should be 15 42
I don't know why it's giving 15 43

Answer 2

put
b = a+3

Answer 3

Tind Indeed, i agree with you (onc again😜). Akshay It seems not well written and logically not the best, that way. At all. Thx for sharing. ☺

Answer 4

I want explanation for GCC compiler

Answer 5

I'm not getting how it's giving 43

Answer 6

This was asked in the interview, thats why I am asking for